Contact lenses have been used commercially to improve vision since the 1950s. The first contact lenses were made of hard materials. Although these lenses are currently used, they are not suitable for all patients due to their poor initial comfort and their relatively low permeability to oxygen. Later developments in the field gave rise to soft contact lenses, based upon hydrogels, which are extremely popular today. These lenses have higher oxygen permeability and are often more comfortable to wear than contact lenses made of hard materials. Unlike hard lenses that are manufactured by lathing hard pieces of plastic, malleable soft contact lenses are often manufactured by forming the lens using a two part mold where each half has topography consistent with the desired final lens. Examples of such molds and their methods of production may be found in U.S. Pat. Nos. 4,565,348, 4,640,489, 4,495,313, JP 08025378, and JP 0726644 which are hereby incorporated by reference in their entirety.
These two part molds contain a male member whose convex surface corresponds to the back curve of a finished lens and a female member whose concave surface corresponds to the front curve of a finished lens. To prepare lenses using these molds, an uncured lens formulation is placed between the concave and convex surfaces of the mold halves and subsequently cured. The cured lens and the mold are subsequently treated with a liquid medium in order to release the cured lens from the surface of the mold. Although this is a process is straightforward, there are a number requirements that must be satisfied in order to produce a useable lens. First the material from which the mold is made must have properties that are chemically compatible with the uncured lens formulation. Second, the mold material must be able to withstand the curing conditions and be compatible with such conditions. For example, lenses may be cured by either or both heat and light. If a lens is cured by transmitting light to the uncured polymer, it is important that the lens mold permit the transmission of light at the appropriate wavelength. Third, the mold material must not stick to the cured lens to a degree that prevents release of the cured lens. Often the lenses are produced in a manufacturing environment where it is important for the lenses to removably adhere to the same said of the lens mold upon separation in a repeatable and predictable fashion. Therefore, the selection of appropriate materials to make the molds continues to be a subject of concern to those who produce soft contact lenses.
Others have used materials such as polypropylene, polystryene, polyethylene, polymethyl methacrylates, and modified polyolefins containing an alicyclic moiety in the main chain to prepare two part lens molds. Although these materials are useful, with discovery of different lens formulations, particularly silicone hydrogel lens formulations, other useful mold materials are needed.
Further, new developments in the field have led to contact lenses made from hydrogels and silicone hydrogels that are coated with polymers to improve the comfort of the lenses. Often lenses are coated by treating the cured lenses with a polymer. Recently polymer coated lenses have been produced by coating the surfaces of a two part mold with a polymer, adding an uncured formulation to the coated lens mold, curing the lens, and subsequently releasing the cured lens from the mold where the surface of said cured lens is coated with the polymer that was originally adhered to the surface of the mold. This process is described in further detail in U.S. patent application Ser. No. 09/921,192, filed on Aug. 8, 2001, currently pending, and entitled “Method for Correcting Articles by Mold Transfer,” which is hereby incorporated by reference in its entirety. When using this method of coating a lens, the choice of mold material is even more critical than when one is producing an uncoated lens.
Therefore, there remains an unmet need to produce lens molds that may be used to produce many different types of soft contact lenses. It is this need that the following invention fills.